DTIC ADA231260: Nonintrusive Nitric Oxide Density Measurements in the NASA Langley Arc- Heated Scramjet Engine Test Facility

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by  Defense Technical Information Center

AEDC-TR-90-26 B
Nonintrusive Nitric Oxide Density
Ui Measurementisn the NASA Langley
Arc-Heated Scramjet Engine Test Facility
R. P. Howard, K. L. Dietz, W. K. McGregor,
and
C. C. Limbaugh
Sverdrup Technology, Inc.
January 1991
Final Report for Period April 1, 1988 through June 1, 1990
Approved for public role.aN; distribution is unlimited.
PROP~TY 01: U.S. AIR FORCE
-"rEC~--~N~C~,,L P.EPORTS
AEDC,T F.C.,HNtCALL IBErtY
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ARNOLD ENGINEERING DEVELOPMENT CENTER
ARNOLD AIR FORCE BASE, TENNESSEE
AIR FORCE SYSTEMS COMMAND
UNITED STATES AIR FORCE
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APPROVAL STATEMENT
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Approved for publication:
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1 AGENCY USE ONLY (Leave blank) REPORTDATE /3 REPORTTYPEANODATESCOVERED
I January 1991 | Final, April 1, 1988 -- June 1, 1990
4 TITLEA ND SUBTITLE 5 FUNDING NUMBERS
Nonintrusive Nitric Oxide Density Measurements in the NASA
PE-65807F
Langley Arc-Heated Scramjet Engine Test Facility
C-F40600-85-C-0026
6 AUTHOR(S)
Howard, R. P., Dietz, K. L., McGregor, W. K., and Limbaugh,C. C.,
Sverdrup Technology, Inc., AEDC Group
7 PERFORMINGO RGANIZATION NAME(S) ANDADDRESS(ES) 8 PERFORMINGO RGANIZATION
REPORT NUMBER
Arnold Engineering Development Center/DOT
Air Force Systems Command AEDC-TR-90-26
Arnold AFB, TN 37389-5000
9 SPONSORING~'VONITORINGA GE NCY NAMES(S}A ND ADDRESS(ES) 10 SP O NSORI~IG.4V10N ITO RING
AGENCY REPORT NUMBER
Arnold Engineering Development Center/DO
Air Force Systems Command
Arnold AFB, TN 37389-5000
11 SUPPLEMENTARNYO TES
Available in Defense Technical Information Center (DTIC).
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Approved for public release; distribution is unlimited.
13. ABSTRACT( Maxim um 200 words)
A nitric ox.ide (NO) resonance absorption technique was used to determine average path
integrated NO number densities through the expanded flow of the NASA La_ngr.ey Arc-
Hea{ed Scramjet Test Faci,i.ty. The mo,e traction range= Trom 0.016 to 0.019 (w,m a zu-
p.ercent uncertaintx).for s.~ti¢ temp.eratu.res from 186.fo 320 K.. Absorption was observed.in
me NO gamma_.(u,1) DO.rid that coum not be ac.countea rot at the static flow conditions i.f t.he
NO were at vibrational equilibrium. Using the (0,1) transmittance measuremen.t and the.
number density calculated from the (0,0) transmittance measurement, vibrational
temperatures ranging from 534 to 919 K were ca.lculated with a minimum uncertainty, from
- 15to 21 percent. A nonequilibrium vibrational temperature, 1,100 K, was. calculatea from
a. one-dimensional kin.eti¢ (ODK) chemistry code compared to the 919 K determined from
the measurement. Within.the range of uncertainties of the (0,1) absorpt!on measurementsf
the corresponding NO raoiati.ve transfer code calculations of vibrational temperature, and
the range o.f unce~ainties of the ODK code calculations, there is good agreement in the
resulting vibrational temperatures.
14 SUBJECTT ERMS 15. NUMBEROF PAGES
arc heater resonance absorption 69
NO gamma bands vibrational nonequilibrium
16 PRICEC ODE
nitric oxide vibrational relaxation
17 SECUR ITY CLASSIFICATION 18 SECURITYC LASSIFICATION 119 SECURITYCLASSIFICATION 20 LIMITATION OF ABSTRACT
OF REPORT OF THiS PAGE J OF ABSTRACT SAME AS REPORT
UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED
COMPUTER GE,%ERATED Standa'd Form 298 (Rev, 2-B9)
P~Qc.cr:bedlov ANSI Ste Z39:8
•~ 98 102
AEDC-TR-90-26
PREFACE
The research reported herein was performed by the Arnold Engineering Development
Center (AEDC), Air Force Systems Command (AFSC). Work and analysis for this research
were done by personnel of Sverdrup Technology, Inc., AEDC Group, operating contractor
for the AEDC propulsion test facilities, under Project Number DC80EW. The Sverdrup
Project Manager was K. L. Dietz, and the Air Force Project Manager was C. Tirres. The
data measurement and initial analysis was completed on May I, 1989. Additional analysis
was completed June I, 1990. This report was submitted for publication on December II, 1990.
The authors wish to express their appreciation for the contributions made by G. Burton
Northam, Olin Jarrett, Jr., Scott R. Thomas, R. Wayne Guy, and Randall T. Voland of
the NASA Langley Research Center.
AEDC-TR-90-26
CONTENTS
Page
1.0 INTRODUCTION ...................................................... 5
2.0 APPARATUS .......................................................... 5
3.0 NO RESONANCE ABSORPTION SYSTEM .............................. 6
3.1 Instrumentation ..................................................... 6
3.2 Instrument and Lamp Characteristics .................................. 7
3.3 Theoretical Modeling Code ........................................... 8
4.0 VIBRATION RELAXATION CODE ..................................... 10
5.0 TEST CONDITIONS AND DATA ....................................... 11
6.0 RESULTS ............................................................. 13
7.0 SUMMARY AND CONCLUSIONS ...................................... 15
REFERENCES ......................................................... 15
ILLUSTRATIONS
Figure Page
1. Longitudinal Section View of the NASA Langley Arc-Heated
Scramjet Test Facility Arc-Heater, Plenum Chamber, and
Mach 6 Nozzle (Refs. 3, 4, and 5) ........................................ 17
2. Illustration of the NO Resonance Absorption Measurement System ........... 18
3. Instrument Response Function for the OMA Detector Element 39,
the Second Bandhead of the (0,0) Band ................................... 19
4. Typical Lamp Spectra Before and During a Test ........................... 20
5. Typical Pretest Detector Background and Flow-Field
Emission Plus Background Levels ........................................ 21
6. Time History of the (0,0) and (0,3) Band Signal Levels During
Test R2BI; Typical of the First Nine Tests Described in Table 1 ............. 22
7. Transmittance Data Taken During Test R4B3; Typical of the
First Tests Described in Table 1 .......................................... 23
8. Time History Data of Test R4B4; Typical of the Last
Three Tests Described in Table 1 ......................................... 24
9. Transmittance Data of Test R4BI; Typical of the Last
Three Tests Described in Table 1 ......................................... 25
10. NO Relative Boltzmaun Plot, Test R3B4 .................................. 26
AEDCoTR-90-26
TABLES
Tables Page
lo NASA Langley Arc-Heated Scramjet Test Facility Parameters ............... 27
2. Results of the NO Resonance Absorption Measurement ..................... 28
APPENDIXES
A. Intensified Sificon Photodiode Array Detector ............................. 29
B. Summary of Test Data .................................................. 30
4
AEDC-TR-90-26
1.0 INTRODUCTION
Nitric oxide, NO, is produced in arcs used for heating air to the high temperatures required
for hypersonic aerodynamic and propulsion test facilities. Although there is NO in the flight
environment, its concentration is far below that produced in the test facilities. It is known
that the NO molecule plays a role in the heating of aerodynamic surfaces in hypersonic flow
and an even greater role in the combustion kinetics of hypersonic air-breathing engines (ramjets
and scramjets). Thus, it becomes vitally important to know the concentration of this species
in the test facility flow so that flight performance may be adequately determined from the
ground test results.
An ultraviolet (UV) resonance absorption method developed for measurements of NO
concentration in turbine engine exhausts (Refs. 1 and 2) has been adapted for arc-heated
flows. The concentration in arc-heated flows is on the order of a few percent, whereas the
NO concentration in turbine engine exhausts is generally much lower and on the order of
a few hundred parts per million. At the higher NO densities of the arc-heated flows, the
NO gamma (0,0) band absorption may become saturated, and the NO gamma (0,1) band
can be used. The radiative transfer model, used to determine NO number densities from
transmittance measurements, was extended to include the absorption in this band. Instrument
improvements included using a linear array detector, or optical multichannel analyzer (OMA),
for the spectral dispersing instrument rather than scanning a grating as used in the earlier
work. The instrument response function is an integral part of the radiative transfer model.
The model was extended to include the OMA response function.
Application of the modified instrumentation and data reduction procedures was made
in the NASA Langley Arc-Heated Scramjet Test Facility (Refs. 3 and 4), and path-integrated
NO densities were determined for a number of test conditions. This report describes the
instrument and model extensions and the results of the experimental determinations.
Additionally, comparisons are made to the vibrational distribution predictions of a one-
dimensional relaxation code.
2.0 APPARATUS
The measurements reported herein were accomplished in the NASA Langley Arc-Heated
Scramjet Test Facility with the Mach 6 nozzle. The facility is described in detail in Refs.
3, 4, and 5. A schematic of the arc heater, plenum chamber, and Mach 6 nozzle from these
references is given in Fig. 1. Briefly, approximately 4,700 K total temperature arc-heated
air is mixed in the plenum chamber with a stream of unheated bypass air and expanded through
the contoured square-cross-section Mach 6 nozzle into the test section of the facility. The
throat area is about 8.44 cm2 , and the nozzle expands to an area of about 765 cm2 in an
AEDC-TR-90-28
axial length of 157 cm. A diffuser downstream of the test section reduces the gas velocity
to subsonic velocity. The gas is cooled and exhausted into a vacuum sphere. The airflow
is established seconds before the arc heater is powered on. The facility is operated nominally
45 see/test.
The facility operating conditions for the tests conducted for the present work are given
in Table 1. The tests are labeled using a Run (R) and Batch (B) notation used at the NASA
facility. The "R" denotes a particular facility test period in which the equipment was in
readiness for testing, typically a single day. The "B" denotes an actual set of conditions
at which the facility was operated, and data were collected and numbered sequentially within
the "R" period. Thus, R2B2 data were acquired after R2BI data but in the same test period,
and R3BI data were acquired on a later day. The "main air" is air introduced into the heater.
"Bypass air" is ambient-temperature air used to dilute the arc-heated air in the plenum
chamber. Ht, Tt, and Pt are the facility bulk enthalpy, total temperature, and total pressure,
respectively, in the plenum chamber. "Is and Ps are the test flow free-stream static temperature
and pressure, respectively, at the exit of the nozzle. Ts and Ps of Table I are approximations
of the static temperature and pressure at the position of the resonance absorption measurements
through the nozzle.
3.0 NO RESONANCE ABSOILPTION SYSTEM
The NO resonance absorption system consists of the instrumentation to perform
transmittance measurements and a theoretical radiative transfer modeling code to interpret
NO concentrations from the measurement.
3.1 INSTRUMENTATION
The NO measurement system consists of an NO resonance lamp emission source, fiber
optics and lenses to direct the lamp emissions, and a spectrometer/OMA detector system.
The major components of the NO resonance absorption system instrumentation and its rehtion
to the facility nozzle are illustrated in Fig. 2. The NO radiation source lamp is a DC- excited,
water-cooled, capillary discharge tube. A 12:3:1 gas mixture (by volu.me) of argon, nitrogen,
and oxygen, respectively, flows through the tube at a static pressure of 10 torr. The lamp
discharge is sustained by a current-regulated power supply operating at 11-ma current and
5,000 V with a 207-kQ ballast resistance.
A UV-grade optical fiber (600-~m core) is used to direct the source radiation to the test
airflow. UV-grade fused silica windows provide optical access to the nozzle through two,
2.54-cm-diam ports on the nozzle wall located 5.7 cm below centerline and 43.2 cm from
the nozzle exit as shown in Fig. 1. The source radiation is collimated to a 1.9-cm-diam beam
6
AEDC-TR-90-26
by a lens exterior to the nozzle, passes through the optical ports of the nozzle, and is transmitted
through an identical focusing lens and optical fiber arrangement to the spectrometer receiving
optics. The beam from the fiber is focused onto the spectrometer entrance slit as it is reflected
from an optical bandpass reflection filter. The reflection filter is used to isolate the NO
radiation and reduce the stray light. The peak reflection efficiency of the filter was 91 percent
at 240 nm with a 30-nm full-width-half-maximum (FWHM) bandpass.
The receiver was a 0.32-m Czerny-Turner configuration spectrometer with a 25-/an entrance
slit. The diffracting element was a ruled 1,800 groove/mm plane grating used in first order,
giving a spatial dispersion of 1.52 nm/mm in the exit plane of the spectrometer. The detector
was an EG&G PAR* Model 1421-B, UV-enhanced, intensified silicon photodiode array (See
Appendix A). The detector array had 1,024 pixels (detector elements), each 2.5 mm tall by
25 tan wide on 25-/tm centers. With the detector installed, the FWHM spectral resolution
was 0.19 nm. The spectral range covered by the detector was slightly less than the reflection
filter bandpass and ranged from 223 to 260 nm, which included the NO gamma (0,0), (0,1),
(0,2), and (0,3) vibrational bands.
3.2 INSTRUMENT AND LAMP CHARACTERISTICS
Proper use of the resonance absorption system requires laboratory characterization of
the source and detector. The lamp radiation is the result of a high-voltage discharge. As
described in Ref. 2, it is unreasonable to expect the emitted spectral line intensities to foliow
thermal equilibrium considerations. Rather, the lines must be individually characterized at
the lamp operating conditions. For this calibration, high-resolution spectra of both the (0,0)
and (0,1) bands were measured in the laboratory using a l-m grating spectrometer with a
spectral resolution of 0.0045 nm. A characterization curve as described in Ref. 2 was generated
for each band from the resolved lines. Each curve is a plot of the radiation intensity (Ij,j,,)
divided by the relative line strength (6j,j, ,) versus the upper-state energy (Fj,), where J' and
J" are the rotational quantum numbers of the upper and lower energy states for a transition,
respectively. Intensities for transitions not resolvable within a band are interpolated from
this curve according to the upper-state energy of the rotational transition. These lamp
characterization curves were used in modeling the resource radiation during data analysis.
Also the presence of the argon in the source working gas provides a low level of continuum
in the emitted radiation from the lamp. Consequently, as described in the following, this
continuum was included in the model.
An important instrument characterization necessary to model the absorption measurement
is the instrument response function for each detector element used in the determination of
number density. The normalized response for each element was determined by recording the
signal level of the detector element since a singlet-transition mercury (Hg) line was scanned
AEDC-TR-90-26
across the detector array in the exit plane of the spectrometer. For example, Fig. 3 shows
the relative response for Detector Element 39 (which is located spectrally at the second
bandhead of the (0,0) band). As the Hg line was scanned away from this detector, the response
reduced by one order of magnitude within 2 adjacent detector elements (0.076 nm) and
gradually decreased beyond 4 detector elements. The intensifier component of the detector
is believed to be the cause of a measurable response beyond a few adjacent detector elements.
In the present work, the instrument response for a detector was determined insignificant beyond
20 detector elements. It should be noted parenthetically that the response shown in Fig. 3
for Detector Element 39 is asymmetrical because the element is near the edge of the detector
array. Instrument response functions for detector elements away from the edge were
symmetrical about the center detector element.
3.3 THEORETICAL MODELING CODE
A computer model based on the theoretical line-by-line radiative transfer model for the
NO gamma (0,0) and (0,1) electronic-vibrational bands of the NO molecule was used to analyze
the transmittance measurements through the test media. Generally, for a given total static
pressure, static temperature, and path length, data are reduced by varying the NO concentration
until the calculated and measured transmittances agree. Although the code can be used for
inversion for profiles of plume properties when appropriate data are taken, the present
measurements were for a single line-of-sight. Consequently, the data are reduced as if from
a homogeneous medium with a uniform temperature and pressure. The resulting NO
concentration is interpreted as a single, average concentration over the line-of-sight
measurement volume.
A detailed discussion of the theory and computer code can be found in Refs. 1 and 2.
Theoretical parameters necessary in extending the modeling code to calculate absorption in
the (0,1) band were taken from the literature. The band center wavenumber, 42191.0 cm-,
was used in calculating the line center absorption coefficient. The rotational constant, 1.6783
cm-1 (Ref. 6), is vibrationally dependent. The most recent value, 5.84 x 10 -4, calculated
from Eq. (5) of Ref. 7 was used for the band oscillator strength. The spectral line positions
published by Deezsi (Ref. 8) were used for both the (0,0) and (0,1) bands. The lamp
characteristics for each line as described previously were incorporated into the code to model
the relative intensities of the source rotational transitions.
The modification for the argon continuum required that the spectral region of the bands
be modeled at increments small enough to include spectral features of both the source and
absorption media rotational transitions. The source and absorption transitions were modeled
by Doppler and Voigt profiles, respectively. The intensity of the argon continuum varies
spectrally, but is approximately constant over the spectral region of the instrument response